In recent years, the cable television industry has grown tremendously. As the cable television industry consumer base has grown, it has been increasingly important to minimize breakdowns in cable television systems in order to avoid loss of service to customers. Moreover, with the advent of telephony and data carried on cable television systems, reliability has become even more important because system failures can result in the interruption of emergency phone calls or other critical communications.
Typically, a cable television system includes a location for receiving and distributing program signals, which are broadband radio-frequency “RF” signals (i.e., 5 MHz to 1,000 MHz). This location is commonly known as a headend where incoming program signals are received from sources such as a satellite dish, an antenna, a VCR tape, and the like. For most incoming broadband signal channels, the headend has individual modulators for modulating each of the signals to the appropriate frequency band for its particular channel. The modules each provide output signals that are fed into a combiner network. The combiner network combines all of the signals received from the various channels on one wide band of frequencies. Because signals lose approximately 3 dB (decibels) for every 2 signals combined, the combined signal output must be amplified to compensate for a loss. A high-powered amplifier amplifies the combined signal to produce an amplified combined signal, which is then transmitted to a splitter network. The splitter network divides the amplified combined signal into numerous signals for distribution to multiple locations.
Amplifiers in the headend are prone to breakdowns and operational failures because such amplifiers typically run at high power levels to reduce signal distortion. The high power levels produce heat that can cause degradation of the semi-conductors and, ultimately, amplifier failure. Because the headend may be operated electronically from a remote location, it is often unattended by a human operator. Therefore, service to the affected customers can be delayed until a human operator is dispatched to correct the problem. Such delays are expensive to the cable television industry and result in customer frustration and dissatisfaction.
Switching circuitry has been used to address the problems associated with amplifier reliability (e.g., see U.S. Pat. No. 5,963,843 which is hereby incorporated by reference in its entirety). Switching circuitry provides a means for the cable operator to have a backup signal (e.g., from a back-up amplifier) that can be automatically or manually switched into a system with no down-time should a primary signal (e.g., from a primary amplifier) fail. In this manner, the switching arrangement provides signal redundancy, which helps improve system reliability. Additional improvements to system reliability and system performance are needed.